Rotating and gyrating ball mill



July 3, 1962 L. SYMONS ROTATING AND GYRATING BALL MILL 4 Sheets-Sheet 1 Filed May 27, 1955 Mil 7 3 my? w xfl %6 WI 3 July 3, 1962 Filed May 27, 1955 L. G. SYMONS ROTATING AND GYRATING BALL MILL 4 Sheets-Sheet 3 Zaren fi. ,SymonS July 3, 1962 1.. G. SYMONS ROTATING AND GYRATING BALL MILL 4 Sheets-Sheet 4 Filed May 27, 1955 United States Patent 3,042,322 ROTATING AND GYRATING BALL MILL Loren G. Symons, North Hollywood, Calif., assignor to Nordherg Manufacturing Company, Milwaukee, Wis., a corporation of Wisconsin Filed May 27, 1955, Ser. No. 511,665 1 Claim. (Cl. 241--175) My invention relates to an improvement in grinding methods, and in mechanism for practicing such methods. Onepurpose 18 to provide an improved grinding method 1n which a charge of grinding balls is employed with greater efficiency.

Another purpose is to provide such a method and mechamsm in which the charge of grinding balls is effecting a grinding action substantially continuously during the presence of the material to be ground in a grinding zone.

Another purpose is to provide an improved method in whlch a given charge of balls is employed with a substantlally greater output per time period than is possible with methods and mechanism previously known.

Another purpose is to provide a grinding method and mechanism in which centrifugal force is controllably employed.

Another purpose is to provide an improved method and apparatus for imparting to the balls or elements of the ball tcharge an optimum grinding path and grinding movemen Another purpose is to provide an improved ball mill 1n whlch a given output of ground material can be produced in a mill of substantially smaller size than known mills of equivalent output.

Another purpose is to provide a method and mechamsm in which a plurality of variable factors are so controlled and related as to obtain an improved grinding result.

Another purpose is to provide an improved method or mechanism in which the thrust or force to which the material is subjected substantially exceeds gravity, and in which, in addition to a rotation effective to subject the charge and the material to more than gravital thrust, an additional motion or motions are employed to impart a grinding movement to the charge.

Another object is to provide an improved grinding mill and method in which all the grinding media are grinding at all times.

Another object is to obtain a radical increase in the material ground per horsepower.

Another purpose is to provide an improved method or mechanism in which the charge is subjected, during rotation about a predetermined axis, to additional forces effective to impart relative movement to the individual balls of the charge.

Other purposes will appear from time to time in the course of the specification and claim.

I illustrate my invention more or less diagrammatically in the accompanying drawings wherein:

FIGURE 1 is a perspective view;

FIGURE 2 is a vertical axial section, on an enlarged scale;

FIGURE 3 is a diagrammatic illustration of the contour of the ball track or chamber, as shown in FIGURES 1 and 2;

FIGURE 4 illustrates a variant form of the track in which it is elongated along its axis of rotation;

FIGURE 5 is another diagrammatic showing in which the ball track is radially elongated or enlarged;

FIGURE 6 is a vertical axial section of another form of my invention; and

FIGURES 7, 8 and 9 diagrammatically illustrate crosssections of the load at various positions of the bowl.

Like parts are indicated by like symbols throughout the specification and drawings.

Referring to the drawings, and in considering an improved ball mill adapted to carry out my improved method, I illustrate, as a matter of example, a mill having the following main components:

A generally indicates a normally fixed base mounted on any suitable support.

B indicates a sub-frame or sub-base or rotor or table which, as will later appear, is rotatably mounted upon the base A for rotation about a preferably vertical axis X.

C generally indicates a ball track or grinding chamber assembly or bowl or retainer in which a charge of balls performing the grinding is contained, and within which it moves to perform its grinding function in relation to the material to be ground.

D generally indicates feeding means for feeding the material to be ground into the ball chamber or bowl C.

The bowl C is rotatably mounted on the sub-base B and rotates about an inclined axis Y, which, as shown, for example, in FIGURE 2, intersects the above mentioned axis X, the point of intersection being indicated as at Z in FIGURE 2.

Before describing the details of my method and of the particular means herein illustrated for carrying it out, I wish to emphasize that I obtain my results by controlling and relating a group of factors which, for convenience, I shall call variables.

Considering first the augmented gravity to which the charge of balls and the material to be ground are subjected, I provide the necessary outward thrust against the retainer by rotating the ball-containing chamber or track about its axis Y at a rate sufficient to obtain the desired outward centrifugal thrust of the charge and of the material undergoing crushing against the inner wall or surface of the bowl. The rate of rotation will, of course, vary with different sizes of mill. A satisfactory outward thrust may, for example, be of the order of eight times gravity. However, this may be widely varied and is given as a practical example and not as a matter of restriction. Of course, normal gravity still acts downwardly.

If I were merely to rotate a charge of balls and material undergoing grinding about a given upright axis, I would obtain little or no grinding efliciency, because the charge and material would tend to freeze against the bowl or retainer in an undisturbed equilibrium position, and would thereafter rotate in :unison with the bowl, with little or no relative movement of the various particles and balls involved and thus with no grinding at all. In order to obtain the necessary action of the charge of balls I subject the charge to other forces creating the desired grinding. In the mill herein described I obtain this action as follows.

While rotating the ball housing or bowl at uniform angular velocity about its inclined axis Y, I also rotate the sub-frame or base B about its axis X. I find it advantageous that rotation of the respective elements about their axes should be in opposite directions. As a result of this simultaneous reverse rotation about dilferent but intersecting axes I give the charge of balls a grinding action between the balls and the bowl, and between individual balls. It will be understood that I may vary the angular relation between the two axes. I may also vary the rotational speed of the sub-base B about the axis X, and may independently vary the rate of rotation of the bowl or housing C about the axis Y. These factors may vary with the radius of the bowl, and the size of the bowl may be widely varied, to grind more or less material.

I may also vary the shape or form of the bowl. I illustrate, in FIGURES l and 2, a bowl which is generally spherical and concentric with the intersection Z between the axes X and Y. In FIGURE 4, I diagrammatically illustrate an axial departure from sphericity, and in FIG- URE 5, I illustrate diagrammatically a radial departure from sphericity. As a matter of fact, I find that I can substantially vary the contour of the track C while maintaining a practical operation of my method. I may even employ conic faces.

Referring to the specific structure of FIGURES 1 and 2, I may employ any suitable frame elements 1, which may, for example, be I-beams or channel beams, suitably connected, for example, by a top plate 2 and transversely extending angles 3 and 4. The top plate 2 is shown as apertured as at 5, and as associated with a discharge chute shown as including an inclined plate 6 and an upper inclined continuation or extension thereof 7. Any material received on the plate portions 6 or 7 will flow downwardly over the lower discharge edge 3 to any suit able receiving or disposal means, not herein shown. I illustrate an upper circumferential flange or wall 10 which may receive a suitable housing 11 having a cover plate 12 apertured as at 13 to permit the entry of any suitable downspout or feed chute 14.

Considering now the supporting and driving means for the rotated portion of the structure, I illustrate a normally fixed bearing sleeve 24 This sleeve extends to and may form part of any suitable gear housing having a bottom member 21 and side member, or members 22, shown as provided with a connecting top plate or flange 23. It will be understood that the member 26 and its associated gear housing 21, 22, 23, may be mounted on or suitably secured to the base frame, for example, by at tachrnent to the transversely extending angles 3 and 4.

24 generally indicates a shaft to which is keyed a suitable driving element or pulley 25 which may be driven by belts 26 from any suitable motor means or power source, such as the motor 27. The shaft 24 is mounted in suitable bearing assemblies 28 and 29 and carries gears or pinions 30, 31, of different diameters. The pinion 30 meshes with the gear 33 on the vetrical shaft 32 mounted for rotation about the axis X. It rotates within a hollow sleeve 34 rotatable in bearing assemblies 35 and 36 within the fixed sleeve 20. The hollow sleeve 34 is driven through the gear 37 in mesh with the upper and smaller pinion 31 of the shaft 24. 38 and 39 are any suitable bearing assemblies interposed between the inner shaft 32 and the outer hollow shaft 34. It will be understood that, in response to the above described drive, they are rotated simultaneously, but at different rates of rotation, in response to rotation of the shaft 24. Mounted on and preferably unitary with the hollow rotated sleeve or shaft 34 is the sub-base or cross-head 40. In response to or in unison with the rotation of the hollow sleeve or shaft 34 the cross-head 40 rotates about the axis X. Within the hollow of the cross-head 40 I illustrate the bevel pinion 41 keyed to the upper end of the solid shaft 32, and therefore rotatable within the cross-head 40. I illustrate the cross-head 40 as, for convenience, having an upper portion or assembly 42 which extends upwardly as the hollow sleeve 43. Rotatable within it is the shaft 44 which rotates about the axis Y. This shaft is mounted for rotation with the ball track element C, or, rather, the ball track element C rotates with and as a result of the rotation of the shaft 44. 45 indicates a suitable bottom bearing assembly between the sleeve 43 and the below described ball track, and 46 is a suitable upper bearing assembly. The bevel pinion 47 at the lower end of the shaft 44 meshes with the bevel pinion 41 at the upper end of the shaft 32. In response to rotation of the shaft 24 it will be understood that the cross-head 40 is rotated about the axis X, and the ball housing assembly C is rotated in an opposite direction of rotation about the axis Y. I may employ any suitable means for varying the relative speeds of rotation about the two axes. Since the details do not of themselves form part of this invention, I do not show them. It will be understood, for example, that the gears or pinions 30, 31, 33, 37, 41 and 47 may all be removed and replaced by others of slightly different diameter, thereby controlling the relative rotational speeds about the two axes.

In connection with the structure as shown, I illustrate a bowl or grinding chamber wall 50 which is generally spherical and formed about the center Z where the axes X and Y intersect. Under some circumstances, I find it preferable to vary from this sphericity. I illustrate, diagrammatically, in FIGURES 3, 4 and 5, a possible range of variations. In FIGURE 3 the track 50' is shown as generally spherical. In FIGURE 4 I illustrate it as varying from this sphericity by an axial elongation. In FIGURE 5, on the contrary, I depart from sphericity in the direction of an increase in radius about the central part of the track. It will be understood that the grinding chamber or member can be widely varied from the spherical, a spherical or generally spherical shape not being essential.

Regardless of the contouring of the bowl itself, I find it advantageous to have an upper end member 51 which may include a central, generally conic wall 52 terminating in an aperture 53. The parts are so proportioned that at no position is the wall 52 or the aperture edge 53 in contact with the downspout or feeding member 14. I illustrate the bottom of the ball track or bowl or grinding chamber as closed by a bottom member 55 which is connected by the sleeve portion 56 with the shaft 44. In the particular form of my device shown in FIGURE 2, I illustrate, also, an outer sleeve, or axial discharge tube, or dam 60, 61. It will be understood that I prefer to have this dam adjustable as to height. For example, the upper section 61 may be removably secured and may readily be removed when the feed distributing plate 70 is removed from the top of the shaft 44. When the upper sleeve extension 61 is in position the ground particles flow over its upper edge in the direction of the arrows of FIGURE 2.

I do not illustrate any specific means for removably supporting the sleeve extension 61, since it will be understood that any suitable means for varying the height of the discharge lip 61a may be employed. It will be understood, also, that the sleeve portions 60 and 61 may be apertured intermediate their ends, or may be entirely dispensed with. In the structure as shown in FIGURE 2, however, the material which passes over the discharge lip flows downwardly through the tube or sleeve 60, to any suitable discharge aperture or apertures, such as 62, 63. If the members 60 and 61 are dispensed with, the openings 63 do not have to be provided with any surrounding duct walls 63a, such as are shown in FIGURE 2. It will be understood, also, that the location of the discharge aperture or apertures and their shape may be varied, depending upon the needs of a particular installation or of a particular material to be ground.

In FIGURE 6, I have shown a variant form of mill having generally upright and inclined axes X and Y intersecting at the grinding chambers center Z. The basic parts or elements are broadly similar to those of FIG- URE 2, and include a normally fixed base A supporting a sub-frame or rotor B with a ball track or grinding cham ber C and a material feeding means D, all disposed generally in the same relationship as in FIGURE 2.

The base A is shown as including a gear box 71 which supports a generally upright post or shaft 72 rigidly fixed or wedged by a tapered portion 73 in a box or journal 74 by a suitable nut 75 or the like.

A bearing assembly 76 is shown as fixed around a suitably shouldered portion 77 of the post and carries suitable gears or pinions 78 and 79 which are bolted or otherwise suitably interlocked. The lower gear 79 meshes with a pinion 80 keyed to an input shaft 81 which is supported on a suitable boss or journal 82 by appropriate bearings 83 with a suitable cover plate 84.

The upper pinion or gear 78 meshes with a pinion 85 fixed on an inclined shaft 86 rotatably supported by suitable bearings 87 and 88 in the sub-frame or rotor B.

The sub-frame or rotor is suitably counterweighted such as at 89 and 90 and is rotatably mounted on the supporting post or shaft 72 by suitable bearing units 91 and 92. A seal 93 is effected between the rotor or subframe and a cover 94 on the gear box. The rotor may be driven by a suitable pinion or ring gear 95 bolted or otherwise suitably connected to the counter-weighting at 96 which meshes with a pinion 97 on a second input shaft 98 which is rotatably supported in a suitable boss or journal 99 by bearings 100.

The housing 101 surrounds the bowl or grinding chamber and supports the feed means or chute D. The housing 101 may be removably mounted as shown in FIGURE 6 or it can be permanently connected or formed as an integral part of the gear box or base.

The bowl or chamber C is shown as generally spherical in :FIGURE 6 although it could be one of the other forms previously shown. A conical wall 102 or the like extends downwardly from the upper opening and is removably connected by bolts or the like.

The inclined shaft 86 has a central disc or shoulder portion 103 with a plurality of legs or spokes 104 connected to a ring 105 which fits into or against a shoulder or flange 106 formed on the bottom of the ball track. The upper end of the inclined shaft carries a feed distributing plate 107 which opposes the inlet feed or chute D.

The discharge opening 108 in the bottom of the bowl may be covered by a screen type medium 109 which includes a plurality of ring members 110 decreasing in diameter upwardly and each resting on or connected to a plurality of spoke-type members 111. Sleeve 112 with a flange 113 is forced down against the spokes by a collar member 114 which is threaded on the inclined shaft at 115.

-In this form the basic operation is much the same as in that of FIGURE 2. Any suitable drive can be connected to one or both of the two input shafts, such as separate motors or the like. The sub-frame or rotor is rotated in the opposite direction from the bowl or grinding chamber. Suitable lubrication can be provided through the center shaft at 116. The bowl or chamber, while shown as a single piece, may be in halves or several portions, either welded or bolted together.

A centrifugal force to arrange the balls and material around the bowl or ball track is set up by rotating the chamber about the inclined axis Y. The rotor is at the same time rotated in the opposite direction about the vertical axis X at a speed sufiicient to create motion between the balls and the bowl, and between the elements of the load.

One effective way of operating the device, as shown in the various figures, is to rotate the bowl and rotor at suitable rotational speeds but in opposite directions. Each element of the ball and material load will be subjected to lifting and lowering cycles at a rapid rate.

It will be realized that whereas I have described a practical method, and have described and shown a practical structure for carrying it out, nevertheless many changes may be made in method steps and characteristics, and in size, shape, number and disposition of parts of the illustrated structures without departing from the spirit of my invention. I therefore wish my description and drawings to be taken as in a broad sense illustrative or diagrammatic rather than as limiting me to my specific structure. For example, the grinding member need not be spherical or generally spherical but can be made in a wide variety of elongated shapes. It will be understood, for example, that the particular mode of mounting the moving parts and the particular means for driving the moving parts are illustrative rather than restrictive. I may, for example, employ individual motors for rotating the shafts 32 and 44 in the form of FIGURE 2, rather than to drive them from gearing from a single motor, as shown herein.

While it is convenient to use a vertically axised machine, even a horizontally axised machine is operable.

Whereas, in FIGURE 2, I illustrate a means for controlling the level of escape of the ground particles, the sleeve 60, 61 of variable height, it will be understood that the sleeve may be completely or partially omitted. For example, I may employ a coil spring or conical rings as a discharge controlling means to prevent the escape of the balls of the charge with the ground material. Whereas a coil spring is satisfactory as a means to prevent or limit such escape, any other suitable means may be employed.

Whereas, in FIGURE 2, I illustrate a three-part ball track member, including the elements 51, 50 and 55, I illustrate, in FIGURE 6, a single ball track element or member. I find it important that the ball track member be readily removable and replaceable. For example, in the structure of FIGURE 6 the ball track member C can be removed unitarily and quickly from the hub structure or shaft with which it rotates. It is shown as having an inwardly, conically surfaced flange 106 opposed to and conforming to a centering flange mounted on the central disc or hub 103- of the inclined shaft 86. The bowl or ball track member C can readily be removed upon removal of the distributing plate 107 and the collar 114 through which a downward thrust is exerted against the cage or screen structure, generally indicated at 109, and, thus, against the lower edge of the ball track member. When the ball track member is worn in use it may thus be bodily upwardly removed and replaced.

The use and operation of my invention are as follows:

Stated broadly, my method includes using: a confining member or bowl, within which the load of balls and material undergoing grinding is confined. The rotation of this member about its axis creates the grinding force or pressure between load and bowl, and between the balls of the load. The gyration of the bowl about a central point causes movement of the load in relation to the inner surface of the bowl, and, at the same time, causes relative movement of the elements of the medium. Thus the simultaneous rotation and gyration of the bowl creates, throughout the entire load, pressure and motion sufficient to grind the hardest particle.

The device can be used as a batch grinder, either dry or wet, and it may be used as an air swept grinder by appropriate air connections of any suitable type, the details of which, for clarity, have not been shown, as I consider them conventional.

While the shape of the bowl may be varied, I show it herein as generally spherical.

I claim:

In a grinding mill, a base, a sub-base mounted thereon for rotation about a generally upright first axis, a hollow bowl mounted on a shaft extending upwardly from the sub base for simultaneous rotation about its axis inclined at a predetermined angle to and intersecting the first axis, the bowl having a top opening surrounding the first axis in all bowl positions, means disposed in the first axis to deliver a generally constant stream of material to be ground normally through said top opening into the interior of the bowl in the general direction of the intersection of the two axes, a body of grinding media in the interior of the bowl, means located entirely below the open top of the bowl to drive said rotary sub-base and said bowl shaft for rotating the bowl simultaneously about both axes at a speed efiective to maintain the media and the material undergoing grinding centrifugally against the inner surface of the bowl with a thrust of the order of several times gravity, and at the same time to impart to the media and material a substantial wave-like movement across the equator of the bowl, and a generally annular concave discharge -at an end of the bowl, surrounding but radially spaced from the bowl axis, formed and adapted to permit the escape of ground material along and from the inner surface of the bowl, while resisting the passage of the media.

References Cited in the file of this patent UNITED STATES PATENTS Pendleton Feb. 24, 190-3 8 Symons Feb. 6, 1951 Weston June 8, 1954 Youngnickel July 26, 1955 Limb July 9, 1957 FOREIGN PATENTS Germany Nov. 11, 1938 Great Britain Nov. 27, 1953 

